The invention relates to a circular formwork with at least one formwork work element, which has a formwork shell having an adjustable curvature and which has braces and/or at least one support, which supports the formwork shell, which has a U-shaped, V-shaped, or trapezoidal cross section that is open to the supported formwork shell and which has fastening flanges on its edges facing the formwork shell for connecting to the rear side of the formwork shell, and with a girder attaching to the braces and to the support or supports at a distance from the formwork shell, wherein the effective length of the girder is adjustable in order to change the curvature of the formwork shell.
Such a formwork with several supports acting as reinforcement, as well as with edge crosspieces similarly acting as reinforcements, is known from DE 24 26 708 C3 or EP 0 514 712 B1 and has proven to be effective. In the formwork and the formwork elements according to DE 24 26 708 C3, the girder attaches to each support, but not to the edge crosspieces, while in the formwork according to EP 0 514 712 B1, there is also a girder between a support near the edge and another reinforcement in the form of an edge crosspiece and the girder has an adjustable effective length.
Here, the support is attached with screws engaging directly in the formwork shell, that is, such an attachment is possible only when the formwork shell has a sufficient thickness. In addition, for the case, in which the screw head is countersunk into the surface of the formwork shell facing the concrete, a corresponding mark is later produced on the concrete surface.
In a formwork shell composed of wood or laminated wood, this shell is also exposed to relatively high wear and tear.
Such a formwork is also known from U.S. Pat. No. 4,619,433, wherein the fastening flanges of the support have an obtuse-angled cross section and the fastening screws engage in the point of this angle. According to the size of the screw head or the nut and/or a plain washer, the flanges are more or less straightened and if necessary pressed into a wooden plate.